When you’re passing 48,000 or even 96,000 audio samples between digital devices every second, the exact timing is critical. The sync only has to be off by a microscopic amount to create bad clicking noises in your audio
To prevent this happening, every device agrees to let one device be the clock master, and they all lock to its crystal clock instead of their own. That’s why the Clock Source setting in iConfig’s Audio Info tab exists.
Normally you’d leave this set to Internal (the default) and all the computer devices lock to the interface. Unless you are working with Aggregate Devices you should have no need to change this and we recommend you leave it on the Internal setting.
Note that iPads and iPhones will just lock to the interface they’re connected to, so there should be no problem there either.
If you are using an Aggregate Device you might need to change this however. Aggregate devices are audio interfaces that are combined in your computer so your music software sees one "virtual" interface with the total number of ins and outs from the real interfaces. For example the following setup – an aggregate device with an iConnectAUDIO2+ and an iConnectMIDI4+.
Which interface should be the clock source? Given a choice, you’d generally make the interface doing the analog/digital conversion the master. That would be the iConnectAUDIO2+, so that’s how we set it in Audio MIDI Setup, the Mac’s configuration program. Aggregate devices are created automatically in Windows – it has no configuration program, so you’re not given a choice.
Either way, you need to go to iConfig’s Audio Configuration tab and tell the iConnectMIDI4+ that it’s no longer boss. More specifically, you have to make the computer doing the aggregating the boss:
If you've never heard clicks and pops, well, good. That's normal, because the factory default setup is good for 95% of all setups. But if you have a setup with, say, aggregate devices on two computers and are having issues then the best advice is to try the available clock schemes until you find the one that works.